[OJS] Problems with DOI generation with default patterns

we had the problem described here, in particular we have a journal that had the default pattern DOI assignation set, but no use of journal number (%v).
In OJS 3.1 the DOI plugin created a DOI despite the use or not of the volume number, but in OJS 3.2 the DOI is not created at all.
We can solve using custom pattern with no %v, but we think this is a bug.
Best regards